Magnetic Effects of Electric Current Chapter Wise Important Questions Class 10 Science
Describe an activity to show that the magnetic field lines produced when current is passed through the circular coil.
Answer.
Aim : To study the characteristics of magnetic field produced by a current carrying circular coil at its centre.
Apparatus Required : Rectangular cardboard having two holes, Thick copper circular coils of different radii having known number of turns, key, battery, rheostat, stand, iron filings.
Procedure :
Pass the coil through the two holes of cardboard in such a way that half of the loop is above the cardboard and remaining part should be below it and normal to the plane of cardboard.
Sprinkle iron filings uniformly on the cardboard.
Allow the current to pass though the coil by inserting plug in the key.
Note the pattern of iron filings that emerges on the cardboard after tapping gently a few times. (Observation).
Place the compass at any point over the pattern of field. Observe the direction of needle. (Observation 2).
Observations :
(a) Iron filings are arranged in the form of concentric circles.
(b) The concentric circles become larger and larger as we move away from the wire.
(c) At the centre of loop, lines are almost straight and perpendicular to the plane of the loop.
Conclusion :
The concentric circles at every point of a current carrying circular loop represent the magnetic field around it.
Magnetic field line close to the axis of loop is straight and is perpendicular to the plane of the coil.
Field lines keep on diverging as we move away from the centre of loop.
- What is meant by solenoid? How does a current carrying solenoid behave? Give its main use.
Answer. Solenoid: A coil of many circular turns of insulated copper wire wound on a cylindrical insulating body (i.e., cardboard etc.) such that its length is greater than its diameter is called solenoid.
3.What are magnetic field lines? Justify the following statements
(a) Two magnetic field lines never intersect each other.
(b) Magnetic field lines are closed curves.
Answer.
Magnetic field lines: It is defined as the path along which the unit North pole (imaginary) tends to move in a magnetic field if free to do so.
(a) The magnetic lines of force do not intersect (or cross) one another. If they do so then at the point of intersection, two tangents can be drawn at that point which indicates that there will be two different directions of the same magnetic which field, i.e. the compass needle points in two different directions which is not possible.
(b) Magnetic field lines are closed continuous curves. They diverge from the north pole of a bar magnet and converge its south pole. Inside the magnet they move from south pole to north pole.
Q: Why and when does a current carrying conductor kept in a magnetic field experience force? List the factors on which direction of this force depends?
Answer. The drifting of free electrons of a conductor in a definite direction causes the current to flow through it. When such conductor is placed in a uniform magnetic field, each drifted electron of a conductor experience a magnetic force. This force is collectively experience by a conductor as a whole. Hence a current carrying conductor kept in a magnetic field experience a force. The direction of magnetic force depends on
(i) direction of current through the conductor, and
(ii) direction of magnetic field.
Q: How is the strength of magnetic field near a straight current-conductor
(i) related to the strength of current in the conductor?
(ii) is affected by changing the direction of flow of current in the conductor?
Answer.
(i) The strength of magnetic field around a straight current conductor increases
on increasing the strength of current in the conductor or vice versa.
(ii)The direction of magnetic field around a straight current carrying conductor gets reversed if the direction of current through that conductor is reversed.
Q::(a) Describe an activity to demonstrate the pattern of magnetic field lines around a straight conductor carrying current.
(b) State the rule to find the direction of magnetic field associated with a current carrying conductor.
(c) What is the shape of a current carrying conductor whose magnetic field
pattern resembles that of a bar-magnet ?
Answer.
(a) Aim : To study the magnetic field due to a straight current carrying conductor.
Apparatus Required : A thick conducting wire, battery, rheostat, magnetic needle, ammeter (0-5 A), key, a cardboard, a stand to hold the wire, iron filings and sprinkler of iron filings.
Procedure :
Attach the thick wire through a hole at the middle of the cardboard and clamp it in a stand.
Attach the ends of the wire through a key, variable resistor and an ammeter on either side of a battery and hold it vertically and perpendicularly to the board.
Spread the iron filings uniformly on the cardboard and place the magnetic needle on the board.
Close the key and tap the cardboard slightly and observe the orientation of iron filings.